1. Field of the Invention
The present invention relates to a transgenic pig for overexpressing heat shock protein 70.
2. Description of the Prior Art
When exposed to nonlethal heat shock, a variety of organisms and cells acquire transient resistance to subsequent exposures to elevated temperatures. This phenomenon has been termed thermotolerance. Heat shock protein (hereafter HSP) 70 has been described as playing an important role in thermoresistance. HSP70 also is closely related to food intake, growth rate and backfat thickness of pigs. HSP is synthesized in cells in response to an increase of temperature above normal physiological levels, or following exposure to a variety of toxic agents. Recently, elevated expression of HSP70 and other HSPs has been observed in cells and tissues under conditions representative of human diseases, including ischemia, oxidant injury, immunology and infectious diseases (Marber, et al., 1995, J. Clin. Invest. 95:1446-1456 and Kiang et al., 1998, Pharmacal. Ther. 80:183-201). The increased expression of these stress proteins could represent an acute response to altered physiological states, as well as chronic adaption to some diseases. The primary function of these stress responses is thought to be cytoprotective. For example, overexpression of HSP70 alone was demonstrated to protect cells from thermal injury and to increase cell survival. By overexpressing rat inducible HSP70, postimplantation murine embryos were protected from heat treatment (Mirkes et al., 1999, Developmental Dynamics, 214:159-170). The protective role of HSP70 was demonstrated clearly by recent studies with transgenic mice in which overexpression of human or rat inducible HSP70 protected myocardium from ischemia reperfusion injury (Marber, et al., 1995, J. Clin. Invest. 95:1446-1456; and Plumier, et al., 1995, J. Clin. Invest., 95:1854-1860).
Most studies concerning HSP70 were performed in vitro or in mice or rat models. However, since the in vitro model and the rat model are far from the human, they cannot be successfully applied in human. There is still a need to develop an animal model close to human for determining the effect of the HSP.